Systems and methods related to multiple degree of freedom force sensors are disclosed. One aspect of the disclosure provides a load sensor. The load sensor comprises a first plate and a second plate, a plurality of single-axis load cells including first, second, and third single-axis load cells, wherein each of the first, second, and third single-axis load cells is disposed between the first plate and the second plate and is oriented along a first axis, and a plurality of constraint joints coupled to the first plate and the second plate, the plurality of constraint joints configured to inhibit translation of the first plate relative to the second plate in directions perpendicular to the first axis and configured to inhibit rotation of the first plate relative to the second plate about the first axis.
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1. A load sensor, comprising:
a first plate and a second plate;
a plurality of single-axis load cells including first, second, third, and fourth single-axis load cells, wherein each of the first, second, third, and fourth single-axis load cells is disposed between the first plate and the second plate and is oriented along a first axis, wherein each of the first, second, third, and fourth single-axis load cells is disposed at a corner of the first plate; and
a plurality of constraint joints coupled to the first plate and the second plate, the plurality of constraint joints configured to inhibit translation of the first plate relative to the second plate in directions perpendicular to the first axis and configured to inhibit rotation of the first plate relative to the second plate about the first axis.
19. A robot comprising:
at least one movable limb; and
a load sensor coupled to the at least one movable limb, wherein the load sensor comprises:
a first plate and a second plate;
a plurality of single-axis load cells including first, second, third, and fourth single-axis load cells, wherein each of the first, second, third, and fourth single-axis load cells is disposed between the first plate and the second plate and is oriented along a first axis, wherein each of the first, second, third, and fourth single-axis load cells is disposed at a corner of the first plate; and
a plurality of constraint joints coupled to the first plate and the second plate, the plurality of constraint joints configured to inhibit translation of the first plate relative to the second plate in directions perpendicular to the first axis and configured to inhibit rotation of the first plate relative to the second plate about the first axis.
12. A method for determining one or more forces and/or torques applied to a portion of a robot, the method comprising:
sensing, by a plurality of single-axis load cells including first, second, third, and fourth single-axis load cells oriented along a first axis and disposed between a first plate and a second plate, forces applied to the portion of the robot, wherein the first and second plates are constrained by a plurality of constraint joints disposed between the first plate and the second plate, wherein the plurality of constraint joints are configured to inhibit relative translation between the first and second plates in directions perpendicular to the first axis and are configured to inhibit relative rotation between the first and second plates about the first axis;
determining forces along the first axis based on the sensed output of the plurality of single-axis load cells;
determining moments about second and third axes based on the sensed outputs of the plurality of single-axis load cells, wherein the second and third axes are each perpendicular to the first axis, and wherein the second axis is perpendicular to the third axis; and
adjusting an operation of the robot based, at least in part, on the determined forces and moments.
2. The load sensor of
3. The load sensor of
4. The load sensor of
5. The load sensor of
an output interface configured to provide signals output from the plurality of single-axis load cells to a processor, wherein the processor is configured to calculate moments about a second axis and a third axis, wherein the second and third axes are each perpendicular to the first axis, and wherein the second axis is perpendicular to the third axis.
6. The load sensor of
7. The load sensor of
8. The load sensor of
9. The load sensor of
10. The load sensor of
11. The load sensor of
13. The method of
14. The method of
15. The method of
16. The method of
17. The method of
18. The method of
21. The robot of
22. The robot of
23. The robot of
24. The robot of
25. The robot of
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This application claims the benefit under 35 U.S.C. § 119(e) of U.S. provisional application Ser. No. 62/949,406, filed Dec. 17, 2019, and entitled “Three Degrees of Freedom Force Sensor”, the disclosure of which is incorporated by reference in its entirety.
A robot is generally defined as a reprogrammable and multifunctional manipulator designed to move material, parts, tools, or specialized devices through variable programmed motions for a performance of tasks. Robots may be manipulators that are physically anchored (e.g., industrial robotic arms), mobile robots that move throughout an environment (e.g., using legs, wheels, or traction-based mechanisms), or some combination of a manipulator and a mobile robot. Robots are utilized in a variety of industries including, for example, manufacturing, transportation, hazardous environments, exploration, and healthcare.
One aspect of the disclosure provides a load sensor. The load sensor comprises a first plate and a second plate, a plurality of single-axis load cells including first, second, and third single-axis load cells, wherein each of the first, second, and third single-axis load cells is disposed between the first plate and the second plate and is oriented along a first axis, and a plurality of constraint joints coupled to the first plate and the second plate, the plurality of constraint joints configured to inhibit translation of the first plate relative to the second plate in directions perpendicular to the first axis and configured to inhibit rotation of the first plate relative to the second plate about the first axis.
In another aspect, the plurality of constraint joints includes at least one spherical constraint.
In another aspect, the at least one spherical constraint is disposed at a centroid of the plurality of single-axis load cells.
In another aspect, the plurality of single-axis load cells further includes a fourth single-axis load cell, wherein the fourth single-axis load cell is disposed between the first plate and the second plate and is oriented along the first axis.
In another aspect, each of the plurality of single-axis load cells is disposed at a corner of the first plate.
In another aspect, the plurality of single-axis load cells are configured to measure forces along the first axis.
In another aspect, the load cell further comprises an output interface configured to provide signals output from the plurality of single-axis load cells to a processor, wherein the processor is configured to calculate moments about a second axis and a third axis, wherein the second axis and the third axis are each perpendicular to the first axis, and wherein the second axis is perpendicular to the third axis.
In another aspect, each of the plurality of single-axis load cells is coupled to the first plate and the second plate through spherical constraints.
In another aspect, each of the plurality of single-axis load cells is coupled to the first plate and the second plate through unidirectional constraints.
In another aspect, each of the plurality of single-axis load cells is configured to measure both compressive and tensile forces along the first axis.
In another aspect, the plurality of single-axis load cells further includes a fifth single-axis load cell oriented along a second axis perpendicular to the first axis.
In another aspect, the load cell further comprises a dual-axis load cell oriented along the second axis and a third axis, wherein the third axis is perpendicular to both the first axis and the second axis.
In another aspect, each of the plurality of constraint joints is co-located with at least one of the plurality of single-axis load cells and/or the dual-axis load cell.
One aspect of the disclosure provides a method for determining one or more forces applied to a portion of a robot. The method comprises sensing, by a plurality of single-axis load cells including first, second, and third single-axis load cells oriented along a first axis and disposed between a first plate and a second plate, forces applied to the portion of the robot. The first and second plates are constrained by a plurality of constraint joints disposed between the first plate and the second plate, wherein the plurality of constraint joints are configured to inhibit relative translation between the first and second plates in directions perpendicular to the first axis and are configured to inhibit relative rotation between the first and second plates about the first axis. The method additionally comprises determining forces along the first axis based on the sensed output of the plurality of single-axis load cells, and determining moments about second and third axes based on the sensed outputs of the plurality of single-axis load cells, wherein the second and third axes are each perpendicular to the first axis, and wherein the second axis is perpendicular to the third axis. The method additionally comprises adjusting an operation of the robot based, at least in part, on the determined forces and moments.
In another aspect, the plurality of single-axis load cells further includes a fourth single-axis load cell. The fourth single-axis load cell is disposed between the first plate and the second plate and is oriented along the first axis. Determining forces along the first axis includes determining forces along the first axis based, at least in part, on the sensed output of the fourth single-axis load cell. Determining moments about the second and third axes includes determining moments about the second and third axes based, at least in part, on the sensed output of the fourth single-axis load cell.
In another aspect, the plurality of single-axis load cells further includes a fifth single-axis load cell oriented along the second axis. The method further comprises determining forces along the second axis based on the sensed output of the plurality of single-axis load cells.
In another aspect, the method further comprises determining forces along the second and third axes based on the sensed output of the plurality of single-axis load cells and/or the sensed output of a dual-axis load cell oriented along the second axis and the third axis.
In another aspect, the method further comprises determining moments about the first axis based on the sensed outputs of the plurality of single-axis load cells and/or the sensed output of the dual-axis load cell.
In another aspect, adjusting the operation of the robot includes adjusting an acceleration of the robot.
In another aspect, adjusting the acceleration of the robot includes limiting a maximum acceleration of the portion of the robot.
In another aspect, wherein adjusting the operation of the robot includes adjusting a trajectory of the robot.
One aspect of the disclosure provides a robot including at least one movable limb and a load sensor coupled to the at least one movable limb. The load sensor comprises a first plate and a second plate, a plurality of single-axis load cells including first, second, and third single-axis load cells, wherein each of the first, second, and third single-axis load cells is disposed between the first plate and the second plate and is oriented along a first axis, and a plurality of constraint joints coupled to the first plate and the second plate, the plurality of constraint joints configured to inhibit translation of the first plate relative to the second plate in directions perpendicular to the first axis and configured to inhibit rotation of the first plate relative to the second plate about the first axis.
In another aspect, the at least one movable limb includes a manipulator arm.
In another aspect, the manipulator arm includes an end-effector, and the load sensor is coupled to the end-effector.
In another aspect, the robot further comprises a processor configured to receive signals output from the load sensor.
In another aspect, the processor is configured to adjust an operation of the robot based, at least in part, on the received signals.
In another aspect, the processor is configured to limit an acceleration of the at least one movable limb based, at least in part, on the received signals.
In another aspect, the processor is configured to adjust a trajectory of the at least one movable limb based, at least in part, on the received signals.
It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein.
Robots are typically configured to perform various tasks in an environment in which they are placed. Generally, these tasks include interacting with objects and/or the elements of the environment. To accomplish such tasks, some robots include one or more arms with end-effectors (e.g., a gripper) controlled to interact with objects in the environment. For instance, a gripper end-effector of a robot may be controlled to pick up objects (e.g., boxes) and arrange the picked up objects on a pallet for shipping, or alternatively, remove objects from a pallet for distribution as part of a logistics application. End-effectors may be coupled to one or more force sensors, configured to measure forces and/or torques applied to the robot when the end-effector interacts with a load (e.g., when the load is lifted by the robot). Force sensors may also be used in combination with other portions of a robot. For instance, a walking robot may include a force sensor in one or more of the robot's limbs (e.g., feet) in contact with an object (e.g., the ground) to sense forces between the limb(s) and the object. Such force sensors often measure forces/torques using six degrees of freedom (6 DOF)—x-y-z axis forces and moments (torques) around each of those axes. In some applications, sensing all six degrees of freedom may not be necessary. For example, sensing three degrees of freedom may suffice in some applications, and the marginal benefit of sensing additional degrees of freedom beyond those that are strictly required for the particular application may not outweigh the increased cost of a conventional 6 DOF sensor compared to a conventional 3 DOF sensor. In applications in which sensing all six degrees of freedom may be desirable or even necessary, a conventional 6 DOF sensor may still be undesirably expensive. Rather, custom sensors tailored to specific applications may be cheaper, simpler, more robust, and more configurable than a conventional sensor.
The inventors have recognized and appreciated that a plurality of single-axis load cells may be used to sense multiple degrees of freedom. Using multiple single-axis load cells may be desirable in that such a system may, for instance, be lower cost, be more modular, use less space, and/or enable a customized sensing solution tailored to a specific set of system constraints and requirements than a conventional integrated 6 DOF sensor. Accordingly, some embodiments are directed to force sensors configured to measure force/torque with fewer than six degrees of freedom. For instance, some embodiments are directed to a three degree of freedom force sensor for use with a robotic system. Some embodiments are directed to force sensors that sense up to six degrees of freedom using a plurality of single-axis (and/or, in some embodiments, dual-axis) load cells. Multi-DOF sensing may be realized through the use of kinematically constrained load cells, as explained in greater detail below.
Example Robotic System
The robot 100 has a vertical gravitational axis Vg along a direction of gravity, and a center of mass (COM), which is a point where the robot 100 has a zero sum distribution of mass. The robot 100 further has a pose P based on the COM relative to the vertical gravitational axis Vg to define a particular attitude or stance assumed by the robot 100. The attitude of the robot 100 can be defined by an orientation or an angular position of an object in space.
The robot 100 generally includes a body 110 and one or more legs 120. The body 110 of the robot 100 may be a unitary structure or a more complex design depending on the tasks to be performed in the environment 10. The body 110 may allow the robot 100 to balance, to sense about the environment 10, to power the robot 100, to assist with tasks within the environment 10, or to support other components of the robot 100. In some examples, the robot 100 includes a two-part body 110. For example, the robot 100 includes an inverted pendulum body (IPB) 110, 110a (i.e., referred to as a torso 110a of the robot 100) and a counter-balance body (CBB) 110, 110b (i.e., referred to as a tail 110b of the robot 100) disposed on the IPB 110a.
The body 110 (e.g., the IPB 110a or the CBB 110b) has first end portion 112 and a second end portion 114. For instance, the IPB 110a has a first end portion 112a and a second end portion 114a while the CBB 110b has a first end portion 112b and a second end portion 114b. In some implementations, the CBB 110b is disposed on the second end portion 114a of the IPB 110a and configured to move relative to the IPB 110a. In some examples, the CBB 110b includes a battery that serves to power the robot 100. A back joint JB may rotatably couple the CBB 110b to the second end portion 114a of the IPB 110a to allow the CBB 110b to rotate relative to the IPB 110a. The back joint JB may be referred to as a pitch joint. In the example shown, the back joint JB supports the CBB 110b to allow the CBB 110b to move/pitch around a lateral axis (y-axis) that extends perpendicular to the gravitational vertical axis Vg and a fore-aft axis (x-axis) of the robot 100. The fore-aft axis (x-axis) may denote a present direction of travel by the robot 100. Movement by the CBB 110b relative to the IPB 110a alters the pose P of the robot 100 by moving the COM of the robot 100 relative to the vertical gravitational axis Vg. A rotational actuator or back joint actuator A, AB (e.g., a tail actuator or counterbalance body actuator) may be positioned at or near the back joint JB for controlling movement by the CBB 110b (e.g., tail) about the lateral axis (y-axis). The rotational actuator AB may include an electric motor, electro-hydraulic servo, piezo-electric actuator, solenoid actuator, pneumatic actuator, or other actuator technology suitable for accurately effecting movement of the CBB 110b relative to the IPB 110a.
The rotational movement by the CBB 110b relative to the IPB 110a alters the pose P of the robot 100 for balancing and maintaining the robot 100 in an upright position. For instance, similar to rotation by a flywheel in a conventional inverted pendulum flywheel, rotation by the CBB 110b relative to the gravitational vertical axis Vg generates/imparts the moment at the back joint JB to alter the pose P of the robot 100. By moving the CBB 110b relative to the IPB 110a to alter the pose P of the robot 100, the COM of the robot 100 moves relative to the gravitational vertical axis Vg to balance and maintain the robot 100 in the upright position in scenarios when the robot 100 is moving and/or carrying a load. However, by contrast to the flywheel portion in the conventional inverted pendulum flywheel that has a mass centered at the moment point, the CBB 110b includes a corresponding mass that is offset from moment imparted at the back joint JB some configurations, a gyroscope disposed at the back joint JB could be used in lieu of the CBB 110b to spin and impart the moment (rotational force) for balancing and maintaining the robot 100 in the upright position.
The CBB 110b may rotate (e.g., pitch) about the back joint JB in both the clockwise and counter-clockwise directions (e.g., about the y-axis in the “pitch direction”) to create an oscillating (e.g., wagging) movement. Movement by the CBB 110b relative to IPB 110a between positions causes the COM of the robot 100 to shift (e.g., lower toward the ground surface 12 or higher away from the ground surface 12). The CBB 110b may oscillate between movements to create the wagging movement. The rotational velocity of the CBB 110b when moving relative to the IPB 110a may be constant or changing (accelerating or decelerating) depending upon how quickly the pose P of the robot 100 needs to be altered for dynamically balancing the robot 100.
The legs 120 are locomotion-based structures (e.g., legs and/or wheels) that are configured to move the robot 100 about the environment 10. The robot 100 may have any number of legs 120 (e.g., a quadruped with four legs, a biped with two legs, a hexapod with six legs, an arachnid-like robot with eight legs, no legs for a robot with a stationary base, etc.). Here, for simplicity, the robot 100 is generally shown and described with two legs 120, 120a-b.
As a two-legged robot 100, the robot includes a first leg 120, 120a and a second leg 120, 120b. In some examples, each leg 120 includes a first end 122 and a second end 124. The second end 124 corresponds to an end of the leg 120 that contacts or is adjacent to a member of the robot 100 contacting a surface (e.g., a ground surface) such that the robot 100 may traverse the environment 10. For example, the second end 124 corresponds to a foot of the robot 100 that moves according to a gait pattern. In some implementations, the robot 100 moves according to rolling motion such that the robot 100 includes a drive wheel 130. The drive wheel 130 may be in addition to or instead of a foot-like member of the robot 100. For example, the robot 100 is capable of moving according to ambulatory motion and/or rolling motion. Here, the robot 100 depicted in
Hip joints JH on each side of body 110 (e.g., a first hip joint JH, JHa and a second hip joint JH, JHb symmetrical about a sagittal plane Ps of the robot 100) may rotatably couple the first end 122 of a leg 120 to the second end portion 114 of the body 110 to allow at least a portion of the leg 120 to move/pitch around the lateral axis (y-axis) relative to the body 110. For instance, the first end 122 of the leg 120 (e.g., of the first leg 120a or the second leg 120b) couples to the second end portion 114a of the IPB 110a at the hip joint JH to allow at least a portion of the leg 120 to move/pitch around the lateral axis (y-axis) relative to the IPB 110a.
A leg actuator A, AL may be associated with each hip joint JH (e.g., a first leg actuator AL, ALa and a second leg actuator AL, ALb). The leg actuator AL associated with the hip joint JH may cause an upper portion 126 of the leg 120 (e.g., the first leg 120a or the second leg 120b) to move/pitch around the lateral axis (y-axis) relative to the body 110 (e.g., the IPB 110a). In some configurations, each leg 120 includes the corresponding upper portion 126 and a corresponding lower portion 128. The upper portion 126 may extend from the hip joint JH at the first end 122 to a corresponding knee joint JK and the lower portion 128 may extend from the knee joint JK to the second end 124. A knee actuator A, AK associated with the knee joint JK may cause the lower portion 128 of the leg 120 to move/pitch about the lateral axis (y-axis) relative to the upper portion 126 of the leg 120.
Each leg 120 may include a corresponding ankle joint JA configured to rotatably couple the drive wheel 130 to the second end 124 of the leg 120. For example, the first leg 120a includes a first ankle joint JA, JAa and the second leg 120b includes a second ankle joint JA, Here, the ankle joint JA may be associated with a wheel axle coupled for common rotation with the drive wheel 130 and extending substantially parallel to the lateral axis (y-axis). The drive wheel 130 may include a corresponding torque actuator (drive motor) A, AT configured to apply a corresponding axle torque for rotating the drive wheel 130 about the ankle joint JA to move the drive wheel 130 across the ground surface 12 along the fore-aft axis (x-axis). For instance, the axle torque may cause the drive wheel 130 to rotate in a first direction for moving the robot 100 in a forward direction along the fore-aft axis (x-axis) and/or cause the drive wheel 130 to rotate in an opposite second direction for moving the robot 100 in a rearward direction along the fore-aft axis (x-axis).
In some implementations, the legs 120 are prismatically coupled to the body 110 (e.g., the IPB 110a) such that a length of each leg 120 may expand and retract via a corresponding actuator (e.g., leg actuators AL) proximate the hip joint JH, a pair of pulleys (not shown) disclosed proximate the hip joint JH and the knee joint JK and a timing belt (not shown) synchronizing rotation of the pulleys. Each leg actuator AL may include a linear actuator or a rotational actuator. Here, a control system 140 with a controller 142 (e.g., shown in
The corresponding axle torques applied to each of the drive wheels 130 (e.g., a first drive wheel 130, 130a associated with the first leg 120a and a second drive wheel 130, 130b associated with the second leg 120b) may vary to maneuver the robot 100 across the ground surface 12. For instance, an axle torque (i.e., a wheel torque TW) applied to the first drive wheel 130a that is greater than a wheel torque TW applied to the second drive wheel 130b may cause the robot 100 to turn to the left, while applying a greater wheel torque TW to the second drive wheel 130b than to the first drive wheel 130 may cause the robot 100 to turn to the right. Similarly, applying substantially the same magnitude of wheel torque TW to each of the drive wheels 130 may cause the robot 100 to move substantially straight across the ground surface 12 in either the forward or reverse directions. The magnitude of axle torque TA applied to each of the drive wheels 130 also controls velocity of the robot 100 along the fore-aft axis (x-axis). Optionally, the drive wheels 130 may rotate in opposite directions to allow the robot 100 to change orientation by swiveling on the ground surface 12. Thus, each wheel torque TW may be applied to the corresponding drive wheel 130 independent of the axle torque (if any) applied to the other drive wheel 130.
In some examples, the body 110 (e.g., at the CBB 110b) also includes at least one non-drive wheel (not shown). The non-drive wheel is generally passive (e.g., a passive caster wheel) and does not contact the ground surface 12 unless the body 110 moves to a pose P where the body 110 (e.g., the CBB 110b) is supported by the ground surface 12.
In some implementations, the robot 100 further includes one or more appendages, such as an articulated arm 150 (also referred to as an arm or a manipulator arm) disposed on the body 110 (e.g., on the IPB 110a) and configured to move relative to the body 110. The articulated arm 150 may have one or more degrees of freedom (e.g., ranging from relatively fixed to capable of performing a wide array of tasks in the environment 10). Here, the articulated arm 150 illustrated in
The articulated arm 150 extends between a proximal first end 152 and a distal second end 154. The arm 150 may include one or more arm joints JA between the first end 152 and the second end 154 where each arm joint JA is configured to enable the arm 150 to articulate in the environment 10. These arm joints JA may either couple an arm member 156 of the arm 150 to the body 110 or couple two or more arm members 156 together. For example, the first end 152 connects to the body 110 (e.g., the IPB 110a) at a first articulated arm joint JA, JA1 (e.g., resembling a shoulder joint). In some configurations, the first articulated arm joint JA, JA1 is disposed between the hip joints JH (e.g., aligned along the sagittal plane Ps of the robot 100 at the center of the body 110). In some examples, the first articulated arm joint JA, JA1 rotatably couples the proximal first end 152 of the arm 150 to the body 110 (e.g., the IPB 110a) to enable the arm 150 to rotate relative to the body 110 (e.g., the IPB 110a). For instance, the arm 150 may move/pitch about the lateral axis (y-axis) relative to the body 110.
In some implementations, such as
The articulated arm 150 may move/pitch about the lateral axis (y-axis) relative to the body 110 (e.g., the IPB 110a). For instance, the articulated arm 150 may rotate about the lateral axis (y-axis) relative to the body 110 in the direction of gravity to lower the COM of the robot 100 while executing turning maneuvers. The CBB 110b may also simultaneously rotate about the lateral axis (y-axis) relative to the IPB 110 in the direction of gravity to assist in lowering the COM of the robot 100. Here, the articulated arm 150 and the CBB 110b may cancel out any shifting in the COM of the robot 100 in the forward or rearward direction along the fore-aft axis (x-axis), while still effectuating the COM of the robot 100 to shift downward closer to the ground surface 12.
With reference to
The controller 142 corresponds to data processing hardware that may include one or more general purpose processors, digital signal processors, and/or application specific integrated circuits (ASICs). In some implementations, the controller 142 is a purpose-built embedded device configured to perform specific operations with one or more subsystems of the robot 100. Additionally or alternatively, the controller 142 includes a software application programmed to execute functions for systems for the robot 100 using the data processing hardware of the controller 142. The memory hardware 144 is in communication with the controller 142 and may include one or more non-transitory computer-readable storage media such as volatile and/or non-volatile storage components. For instance, the memory hardware 144 may be associated with one or more physical devices in communication with one another and may include optical, magnetic, organic, or other types of memory or storage. The memory hardware 144 is configured to, inter alia, store instructions (e.g., computer-readable program instructions) that, when executed by the controller 142, cause the controller 142 to perform numerous operations, such as, without limitation, altering the pose P of the robot 100 for maintaining balance, maneuvering the robot 100, detecting objects, transporting objects, and/or performing other tasks within the environment 10. In some implementations, the controller 142 performs the operations based on direct or indirect interactions with a sensor system 170.
The sensor system 170 includes one or more sensors 172, 172a-n. The sensors 172 may include vision/image sensors, inertial sensors (e.g., an inertial measurement unit (IMU)), and/or kinematic sensors. Some examples of one or more sensors 172 include a camera such as a monocular camera or a stereo camera, a time of flight (TOF) depth sensor, a scanning light-detection and ranging (LIDAR) sensor, or a scanning laser-detection and ranging (LADAR) sensor. More generically, the sensor(s) 172 may include one or more of force sensors, torque sensors, velocity sensors, acceleration sensors, position sensors (linear and/or rotational position sensors), motion sensors, location sensors, load sensors, temperature sensors, pressure sensors (e.g., for monitoring the end-effector actuator AEE), touch sensors, depth sensors, ultrasonic range sensors, infrared sensors, and/or object sensors. In some examples, sensor(s) 172 have a corresponding field(s) of view defining a sensing range or region corresponding to sensor(s) 172. Each sensor 172 may be pivotable and/or rotatable such that the sensor 172 may, for example, change the field of view about one or more axes (e.g., an x-axis, a y-axis, or a z-axis in relation to a ground surface 12). In some implementations, the body 110 of the robot 100 includes a sensor system 170 with multiple sensors 172 about the body to gather sensor data 174 in all directions around the robot 100. Additionally or alternatively, sensor(s) 172 of the sensor system 170 may be mounted on the arm 150 of the robot 100 (e.g., in conjunction with one or more sensors 172 mounted on the body 110). The robot 100 may include any number of sensors 172 as part of the sensor system 170 in order to generate sensor data 174 for the environment 10 about the robot 100. For instance, when the robot 100 is maneuvering about the environment 10, the sensor system 170 gathers pose data for the robot 100 that includes inertial measurement data (e.g., measured by an IMU). In some examples, the pose data includes kinematic data and/or orientation data about the robot 100.
When surveying a field of view with a sensor 172, the sensor system 170 generates sensor data 174 (also referred to as image data 174) corresponding to the field of view. Sensor data 174 gathered by the sensor system 170, such as the image data, pose data, inertial data, kinematic data, etc., relating to the environment 10 may be communicated to the control system 140 (e.g., the controller 142 and/or memory hardware 144) of the robot 100. In some examples, the sensor system 170 gathers and stores the sensor data 174 (e.g., in the memory hardware 144 or memory hardware related to remote resources communicating with the robot 100). In other examples, the sensor system 170 gathers the sensor data 174 in real-time and processes the sensor data 174 without storing raw (i.e., unprocessed) sensor data 174. In yet other examples, the controller system 140 and/or remote resources store both the processed sensor data 174 and raw sensor data 174. The sensor data 174 from the sensor(s) 172 may allow systems of the robot 100 to detect and/or to analyze conditions about the robot 100. For instance, the sensor data 174 may allow the control system 140 to maneuver the robot 100, alter a pose P of the robot 100, and/or actuate various actuators A for moving/rotating mechanical components of the robot 100 (e.g., about joints J of the robot 100).
Example Force Sensor
As discussed above, a robot in accordance with some embodiments includes an end-effector (e.g., end-effector 160) coupled to a force sensor. The force sensor may be configured to determine one or more forces and/or torques applied to the robot when an object (e.g., box 20) is lifted by the robot.
In some embodiments, a force sensor 200 additionally includes a plurality of constraint joints 208, 210 arranged to inhibit one or more degrees of freedom of the two plates 202 and 204 of the force sensor 200. For instance, the constraint joints may be configured to inhibit translation of the first plate 202 relative to the second plate 204 in one or more directions perpendicular to the single axis of the load cells (e.g., the X and Y directions shown in
In some embodiments, load cells 206 may be coupled to the first plate 202 and the second plate 204 through spherical constraints 214. One such embodiment is shown in
In the embodiment of
It should be appreciated that the specific arrangement of load cells depicted in
Furthermore, removing the load sensing capabilities of some of the load cells but retaining the associated kinematic constraints may be associated with a force sensor configured to sense fewer than six degrees of freedom (e.g., an example of which is shown as the three degree of freedom load sensor in
For example, in a first alternative configuration, load cells 305 and 306 may be removed, but their associated kinematic constraints may be maintained. The resulting force sensor may be configured to measure forces along the Z axis and moments about the X and Y axes. As such, the force sensor of the first alternative configuration may be described as a bending/axial force sensor. Such a first alternative configuration may have a configuration and functionality similar to the configuration of the force sensor 200 described in relation to
In a second alternative configuration, load cells 301-304 may be removed, but their associated kinematic constraints may be maintained. The resulting force sensor may be configured to measure forces along the X and Y axes and moments about the Z axis. As such, the force sensor of the second alternative configuration may be described as a shear/torque sensor.
Table 1 summaries the load sensing axes and the kinematic constraint axes associated with each load cell 301-306 for each of the above-described configurations. Note that the primary configuration is denoted “Config. #1”, the first alternative configuration is denoted “Config. #2”, and the second alternative configuration is denoted “Config. #3”.
TABLE 1
Load sensing axes
Kinematic constraint axes
Load
Config.
Config.
Config.
Config.
Config.
Config.
cell
#1
#2
#3
#1
#2
#3
301
Z
Z
n/a
Z
Z
Z
302
Z
Z
n/a
Z
Z
Z
303
Z
Z
n/a
Z
Z
Z
304
Z
Z
n/a
Z
Z
Z
305
Y
n/a
Y
Y
Y
Y
306
X, Y
n/a
X, Y
X, Y
X, Y
X, Y
Other alternative configurations of force sensors may be constructed using the framework of a plurality of single-axis (or dual-axis) load cells and a plurality of kinematic constraints (wherein the load cells themselves may impose all of the kinematic constraints, and/or wherein there are additional kinematic constraints beyond the kinematic constraints imposed by the load cells). The force sensor 300 of
In some embodiments, a force sensor (e.g., force sensor 200, or force sensor 300, or any suitable alternative) may be included in a portion of a limb (e.g., an arm or end-effector attached thereto) of a robotic system (e.g., the robotic system illustrated in
It should be appreciated that a force sensor may also be used in combination with other portions of a robot to sense forces applied to the robot, and that the disclosure is not limited in this regard. For example, a force sensor may be disposed at an ankle joint of a robotic leg, and may be used to measure the forces and/or moments that are transferred from a foot to the remainder of the robotics system as the robotic system locomotes.
One or more forces and/or moments measured by a force sensor may be used, for example, by a controller (e.g., controller 142 of control system 140) to adjust the operation of one or more components of the robot to change its behavior based, at least in part, on the sensed forces and/or moments applied to the robot. For instance, if the force sensor detects that the load lifted by the end-effector is heavy, the speed and/or acceleration of the arm to which the end-effector is attached may be reduced to mitigate the possibility that the load may be dropped and/or to reduce the possibility of an unsafe operating condition of the robot. As another example, a trajectory of the arm may be adjusted based on the sensed load at the end effector.
It should be appreciated that although the term “force sensor” is used herein, sensors described in the present disclosure may be configured to sense forces and/or torques in any suitable number of axes, and that the present disclosure is not limited to sensors that sense only force and not torque. The term “force sensor” is used herein solely for convenience and readability, and should not be construed as limiting. Additionally, the terms “moment” and “torque” are used interchangeably herein.
The computing devices and systems described and/or illustrated herein broadly represent any type or form of computing device or system capable of executing computer-readable instructions, such as those contained within the modules described herein. In their most basic configuration, these computing device(s) may each include at least one memory device and at least one physical processor.
In some examples, the term “memory device” generally refers to any type or form of volatile or non-volatile storage device or medium capable of storing data and/or computer-readable instructions. In one example, a memory device may store, load, and/or maintain one or more of the modules described herein. Examples of memory devices include, without limitation, Random Access Memory (RAM), Read Only Memory (ROM), flash memory, Hard Disk Drives (HDDs), Solid-State Drives (SSDs), optical disk drives, caches, variations or combinations of one or more of the same, or any other suitable storage memory.
In some examples, the term “physical processor” generally refers to any type or form of hardware-implemented processing unit capable of interpreting and/or executing computer-readable instructions. In one example, a physical processor may access and/or modify one or more modules stored in the above-described memory device. Examples of physical processors include, without limitation, microprocessors, microcontrollers, Central Processing Units (CPUs), Field-Programmable Gate Arrays (FPGAs) that implement softcore processors, Application-Specific Integrated Circuits (ASICs), portions of one or more of the same, variations or combinations of one or more of the same, or any other suitable physical processor.
Although illustrated as separate elements, the modules described and/or illustrated herein may represent portions of a single module or application. In addition, in certain embodiments one or more of these modules may represent one or more software applications or programs that, when executed by a computing device, may cause the computing device to perform one or more tasks. For example, one or more of the modules described and/or illustrated herein may represent modules stored and configured to run on one or more of the computing devices or systems described and/or illustrated herein. One or more of these modules may also represent all or portions of one or more special-purpose computers configured to perform one or more tasks.
In addition, one or more of the modules described herein may transform data, physical devices, and/or representations of physical devices from one form to another. Additionally, or alternatively, one or more of the modules recited herein may transform a processor, volatile memory, non-volatile memory, and/or any other portion of a physical computing device from one form to another by executing on the computing device, storing data on the computing device, and/or otherwise interacting with the computing device.
The above-described embodiments can be implemented in any of numerous ways. For example, the embodiments may be implemented using hardware, software or a combination thereof. When implemented in software, the software code can be executed on any suitable processor or collection of processors, whether provided in a single computer or distributed among multiple computers. It should be appreciated that any component or collection of components that perform the functions described above can be generically considered as one or more controllers that control the above-discussed functions. The one or more controllers can be implemented in numerous ways, such as with dedicated hardware or with one or more processors programmed using microcode or software to perform the functions recited above.
In this respect, it should be appreciated that embodiments of a robot may include at least one non-transitory computer-readable storage medium (e.g., a computer memory, a portable memory, a compact disk, etc.) encoded with a computer program (i.e., a plurality of instructions), which, when executed on a processor, performs one or more of the above-discussed functions. Those functions, for example, may include control of the robot and/or driving a wheel or arm of the robot. The computer-readable storage medium can be transportable such that the program stored thereon can be loaded onto any computer resource to implement the aspects of the present invention discussed herein. In addition, it should be appreciated that the reference to a computer program which, when executed, performs the above-discussed functions, is not limited to an application program running on a host computer. Rather, the term computer program is used herein in a generic sense to reference any type of computer code (e.g., software or microcode) that can be employed to program a processor to implement the above-discussed aspects of the present invention.
Various aspects of the present invention may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described in the foregoing and are therefore not limited in their application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.
Also, embodiments of the invention may be implemented as one or more methods, of which an example has been provided. The acts performed as part of the method(s) may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.
Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed. Such terms are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term).
The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” “having,” “containing”, “involving”, and variations thereof, is meant to encompass the items listed thereafter and additional items.
Having described several embodiments of the invention in detail, various modifications and improvements will readily occur to those skilled in the art. Such modifications and improvements are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description is by way of example only, and is not intended as limiting.
Saunders, John Aaron, Geating, Joshua Timothy, Borrell, Adam Henry
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Apr 27 2021 | BORRELL, ADAM HENRY | BOSTON DYNAMICS, INC | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 056200 | /0790 | |
May 04 2021 | SAUNDERS, JOHN AARON | BOSTON DYNAMICS, INC | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 056200 | /0790 | |
May 05 2021 | GEATING, JOSHUA TIMOTHY | BOSTON DYNAMICS, INC | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 056200 | /0790 |
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